1. Field of the Invention
The present invention relates to a tone generating apparatus for use in electronic musical instruments, such as a synthesizer, an electronic piano, an electronic organ, and a single keyboard. More particularly, this invention pertains to an arrangement that permits easy reading of a one-shot waveform in a tone generating apparatus, which reads out tone waveform data from a wave memory to generate a tone signal.
2. Description of the Related Art
In general, a tone generating apparatus (sound source) for use in an electronic musical instrument includes a wave memory in which plural types of tone waveform data corresponding to multifarious types of timbres are provided. In tone generation, tone waveform data in the wave memory which corresponds to a timbre specified by, for example, a panel switch or the like, is selected and is read out at a speed corresponding to a key (i.e., pitch) to produce a tone signal, and this tone signal is supplied to an acoustic circuit to generate a musical tone.
Since the capacity of the wave memory to store tone waveform data is limited, various methods are considered to store tone waveform data in compressed form.
For instance, there is a method which, with respect to one timbre, stores tone waveform data for the attack portion of a musical tone and tone waveform data for the sustain portion of that musical tone separately in the wave memory. With the tone waveform data stored in this method, when tone generation is instructed, the tone waveform data for the attack portion of a musical tone is read out only once, followed by repetitive reading of the tone waveform data for the sustain portion of that musical tone, to produce associated tone signals in order to acquire a predetermined musical tone.
This method can reproduce at high fidelity an intricate and delicate sound contained in the attack portion of a musical tone as well as can produce the sound of the sustain portion of that musical tone with fewer pieces of tone waveform data, while ensuring data compression.
Not every musical tone to be produced by an electronic musical instrument or the like has the aforementioned sustaining sound, but there are not a few cases of non-repeated and only one tone generation in a short period. The latter tone generation is accomplished by reading tone waveform data from the wave memory, from the top to the end, only once, (this way of reading out tone waveform data will hereinafter be called "one-shot waveform reading").
In order to manage the above two reading methods, therefore, a conventional tone generating apparatus has separate circuits for reading out tone waveform data to generate a sustaining sound and for reading out a one-shot waveform.
This complicates the structure of the tone generating apparatus and increases the cost thereof.